Open-chain steroidal glycosides, a diverse class of plant saponins

Mode of molecular interaction of triterpenoid saponin ginsenoside Rh2 with membrane lipids in liquid-disordered phases

Ginsenoside Rh2 (Rh2) is a ginseng saponin comprising a triterpene core and one unit of glucose and has attracted much attention due to its diverse biological activities. In the present study, we used small-angle X-ray diffraction, solid-state NMR, fluorescence microscopy, and MD simulations to investigate the molecular interaction of Rh2 with membrane lipids in the liquid-disordered (Ld) phase mainly composed of palmitoyloleoylphosphatidylcholine compared with those in liquid-ordered (Lo) phase mainly composed of sphingomyelin and cholesterol. The electron density profiles determined by X-ray diffraction patterns indicated that Rh2 tends to be present in the shallow interior of the bilayer in the Ld phase, while Rh2 accumulation was significantly smaller in the Lo phase. Order parameters at intermediate depths in the bilayer leaflet obtained from 2H NMR spectra and MD simulations indicated that Rh2 reduces the order of the acyl chains of lipids in the Ld phase. The dihydroxy group and glucose moiety at both ends of the hydrophobic triterpene core of Rh2 cause tilting of the molecular axis relative to the membrane normal, which may enhance membrane permeability by loosening the packing of lipid acyl chains. These features of Rh2 are distinct from steroidal saponins such as digitonin and dioscin, which exert strong membrane-disrupting activity.

Promising natural products targeting protein tyrosine phosphatase SHP2 for cancer therapy

The development of Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) inhibitors is a hot spot in the research and development of antitumor drugs, which may induce immunomodulatory effects in the tumor microenvironment and participate in anti-tumor immune responses. To date, several SHP2 inhibitors have made remarkable progress and entered clinical trials for the treatment of patients with advanced solid tumors. Multiple compounds derived from natural products have been proved to influence tumor cell proliferation, apoptosis, migration and other cellular functions, modulate cell cycle and immune cell activation by regulating the function of SHP2 and its mutants. However, there is a paucity of information about their diversity, biochemistry, and therapeutic potential of targeting SHP2 in tumors. This review will provide the structure, classification, inhibitory activities, experimental models, and antitumor effects of the natural products. Notably, this review summarizes recent advance in the efficacy and pharmacological mechanism of natural products targeting SHP2 in inhibiting the various signaling pathways that regulate different cancers and thus pave the way for further development of anticancer drugs targeting SHP2.

Integrated evolutionary pattern analyses reveal multiple origins of steroidal saponins in plants

Steroidal saponins are a class of specialized metabolites essential for plant's response to biotic and abiotic stresses. They are also important raw materials for the industrial production of steroid drugs. Steroidal saponins are present in some monocots, such as Dioscorea and Paris, but their distribution, origin, and evolution in plants remain poorly understood. By reconstructing the evolutionary history of the steroidal saponin-associated module (SSAM) in plants, we reveal that the steroidal saponin pathway has its origin in Asparagus and Dioscorea. Through evaluating the distribution and evolutionary pattern of steroidal saponins in angiosperms, we further show that steroidal saponins originated multiple times in angiosperms, and exist in early diverged lineages of certain monocot lineages including Asparagales, Dioscoreales, and Liliales. In these lineages, steroidal saponins are synthesized through the high copy and/or high expression mechanisms of key genes in SSAM. Together with shifts in gene evolutionary rates and amino acid usage, these molecular mechanisms shape the current distribution and diversity of steroidal saponins in plants. Consequently, our results provide new insights into the distribution, diversity and evolutionary history of steroidal saponins in plants, and enhance our understanding of plants' resistance to abiotic and biotic stresses. Additionally, fundamental understanding of the steroidal saponin biosynthesis will facilitate their industrial production and pharmacological applications.

Antimicrobial and antiviral evaluation of compounds from Holoptelea integrifolia: in silico supported in vitro study

Holoptelea integrifolia, also known as the Indian Elm Tree, has been used in Ayurvedic medicine for its medicinal properties. In this study, two biologically active metabolites, 5(6) dihydrostigmast 22en 3-O-β-glucoside (DHS) and 1-O-eicosanoyl glycerol-2'-O-β-galactouronic (EGG), were isolated for the first time from the n-butanol fraction of H. integrifolia using a chromatographic technique and identified by NMR, and HRESI-MS. The antiviral and multidrug-resistant activities of these metabolites were evaluated as well as the n-butanol fraction. The n-butanol fraction of H. integrifolia exhibited weak antiviral effects, but DHS and EGG demonstrated significant antiviral activity against herpes simplex type-1 (HSV-1) and Coxsackie (CoxB4) viruses. Both metabolites showed lower IC50 values than the standard antiviral drug acyclovir, indicating their potency in inhibiting viral replication. EGG showed potent antiviral activity with minimal cytotoxicity at the highest concentration tested, presenting a selectivity index (SI) of 18.18 and 15.58 against HSV-1 and CoxB4 viruses, respectively. A preliminary assessment of the antibacterial activity of the n-butanol fraction and metabolites revealed that DHS had the highest inhibitory potency against drug-resistant strains, including MRSA and Carbapenem-resistant Klebsiella pneumonia. It also exhibited significant inhibitions against Fluconazole-resistant Candida albicans and ESBL - Escherichia coli. DHS displayed the lowest minimum inhibitory concentration (MIC) values, indicating its superiority as an antibacterial agent compared to EGG and the n-butanol fraction. Molecular docking analysis confirmed the antiviral and antibacterial actions of DHS and EGG by demonstrating their strong binding.

Characterization and structure-based protein engineering of a regiospecific saponin acetyltransferase from Astragalus membranaceus

Acetylation contributes to the bioactivity of numerous medicinally important natural products. However, little is known about the acetylation on sugar moieties. Here we report a saponin acetyltransferase from Astragalus membranaceus. AmAT7-3 is discovered through a stepwise gene mining approach and characterized as the xylose C3'/C4'-O-acetyltransferse of astragaloside IV (1). To elucidate its catalytic mechanism, complex crystal structures of AmAT7-3/1 and AmAT7-3A310G/1 are obtained, which reveal a large active pocket decided by a specific sequence AADAG. Combining with QM/MM computation, the regiospecificity of AmAT7-3 is determined by sugar positioning modulated by surrounding amino acids including #A310 and #L290. Furthermore, a small mutant library is built using semi-rational design, where variants A310G and A310W are found to catalyze specific C3'-O and C4'-O acetylation, respectively. AmAT7-3 and its variants are also employed to acetylate other bioactive saponins. This work expands the understanding of saponin acetyltransferases, and provide efficient catalytic tools for saponin acetylation.

Effect of the number of sugar units on the interaction between diosgenyl saponin and membrane lipids

Saponin is the main bioactive component of the Dioscorea species, which are traditionally used for treating chronic diseases. An understanding of the interaction process of bioactive saponins with biomembranes provides insights into their development as therapeutic agents. The biological effects of saponins have been thought to be associated with membrane cholesterol (Chol). To shed light on the exact mechanisms of their interactions, we investigated the effects of diosgenyl saponins trillin (TRL) and dioscin (DSN) on the dynamic behavior of lipids and membrane properties in palmitoyloleolylphosphatidylcholine (POPC) bilayers using solid-state NMR and fluorescence spectroscopy. The membrane effects of diosgenin, a sapogenin of TRL and DSN, are similar to those of Chol, suggesting that diosgenin plays a major role in membrane binding and POPC chain ordering. The amphiphilicity of TRL and DSN enabled them to interact with POPC bilayers, regardless of Chol. In the presence of Chol, the sugar residues more prominently influenced the membrane-disrupting effects of saponins. The activity of DSN, which bears three sugar units, led to perturbation and further disruption of the membrane in the presence of Chol. However, TRL, which bears one sugar residue, increased the ordering of POPC chains while maintaining the integrity of the bilayer. This effect on the phospholipid bilayers is similar to that of cholesteryl glucoside. The influence of the number of sugars in saponin is discussed in more detail.

Inhibiting Angiogenesis by Anti-Cancer Saponins: From Phytochemistry to Cellular Signaling Pathways

Saponins are one of the broadest classes of high-molecular-weight natural compounds, consisting mainly of a non-polar moiety with 27 to 30 carbons and a polar moiety containing sugars attached to the sapogenin structure. Saponins are found in more than 100 plant families as well as found in marine organisms. Saponins have several therapeutic effects, including their administration in the treatment of various cancers. These compounds also reveal noteworthy anti-angiogenesis effects as one of the critical strategies for inhibiting cancer growth and metastasis. In this study, a comprehensive review is performed on electronic databases, including PubMed, Scopus, ScienceDirect, and ProQuest. Accordingly, the structural characteristics of triterpenoid/steroid saponins and their anti-cancer effects were highlighted, focusing on their anti-angiogenic effects and related mechanisms. Consequently, the anti-angiogenic effects of saponins, inhibiting the expression of genes related to vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1-α (HIF-1α) are two main anti-angiogenic mechanisms of triterpenoid and steroidal saponins. The inhibition of inflammatory signaling pathways that stimulate angiogenesis, such as pro-inflammatory cytokines, mitogen-activated protein kinase (MAPKs), and phosphoinositide 3-kinases/protein kinase B (PI3K/Akt), are other anti-angiogenic mechanisms of saponins. Furthermore, the anti-angiogenic and anti-cancer activity of saponins was closely related to the binding site of the sugar moiety, the type and number of their monosaccharide units, as well as the presence of some functional groups in their aglycone structure. Therefore, saponins are suitable candidates for cancer treatment by inhibiting angiogenesis, for which extensive pre-clinical and comprehensive clinical trial studies are recommended.

Advances in the Biosynthesis and Molecular Evolution of Steroidal Saponins in Plants

Steroidal saponins are an important type of plant-specific metabolite that are essential for plants' responses to biotic and abiotic stresses. Because of their extensive pharmacological activities, steroidal saponins are also important industrial raw materials for the production of steroidal drugs. In recent years, more and more studies have explored the biosynthesis of steroidal saponins in plants, but most of them only focused on the biosynthesis of their molecular skeleton, diosgenin, and their subsequent glycosylation modification mechanism needs to be further studied. In addition, the biosynthetic regulation mechanism of steroidal saponins, their distribution pattern, and their molecular evolution in plants remain unclear. In this review, we summarized and discussed recent studies on the biosynthesis, molecular regulation, and function of steroidal saponins. Finally, we also reviewed the distribution and molecular evolution of steroidal saponins in plants. The elucidation of the biosynthesis, regulation, and molecular evolutionary mechanisms of steroidal saponins is crucial to provide new insights and references for studying their distribution, diversity, and evolutionary history in plants. Furthermore, a deeper understanding of steroidal saponin biosynthesis will contribute to their industrial production and pharmacological applications.

Steroidal glycoside profile differences among primary roots system and adventitious roots in Solanum dulcamara

Solanum dulcamara primary and adventitious roots showed qualitative and quantitative differences in their steroidal glycosides profile. This opened new venues to evaluate the bioactivity of these molecules in belowground ecosystems. The Solanum genus is characterized by the presence of steroidal glycosides (SGs) that confer herbivore resistance and serve as drug precursors in the pharmaceutical industry. Solanum dulcamara is a self-compatible, sexually reproducing species that produces seeds after buzz-pollination. In addition, primordia on the stem facilitate clonal propagation via adventitious root (AR) formation. ARs contain aerenchyma being developmentally and morphologically different from primary roots (PRs). Therefore, we hypothesized that ARs and PRs have different SG profiles. Aiming to assess differences in SGs profiles in S. dulcamara roots in relation to their origins and morphologies, we used liquid chromatography coupled to electron spray ionization quadruple time of flight mass spectrometry (LC-ESI-qToF-MS) to profile SGs from PRs and ARs of seven S. dulcamara individuals. Mass fragmentation pattern analysis indicated the presence of 31 SG-type structures, including those with spirostans and furostans moieties. We assigned the 31 structures to 9 classes of steroidal aglycons (SAgls) that differ in hydroxylation and degree of unsaturation. We found that SAgls were conjugated with di-, tri- and tetra saccharides whereby one compound contained a malonylated sugar. Principle component analysis showed that SG profiles of PRs and ARs separated on the first principal component, supporting our hypothesis. Specifically, PRs contain higher number of SGs than ARs with some compounds exclusively present in PRs. Our results reveal a high level of novel chemodiversity in PRs and ARs of Solanum dulcamara. The knowledge gained will deepen our understanding of SGs biosynthesis and their functional role in plant-environment interactions.

Effects of Asparagus officinalis on immune system mediated EAE model of multiple sclerosis

Background

About 5 to 10 percent of the population in developed countries are affected by autoimmune diseases. One of the most important autoimmune disease with high prevalence rate is Multiple sclerosis in which there is currently no definitive cure for it, and most medications such as interferons are used only to limit the disease. The present study aims to investigate the effect of using Asparagus Officinalis fractions in an immune system mediated model of multiple sclerosis.

Material and Methods

Fractionation was performed by maceration using n-hexane, chloroform, chloroform-methanol (9: 1), n-Butanol and methanol solvents from aerial parts of Asparagus Officinalis. Thin layer chromatography, NMR and phenolic component measurement were done and two fractions were selected for checking in MS induced in vivo model.

Results

It was observed that chloroform-methanolic and N-Butanol fractions had higher content of saponin in comparison of other extracts. Also, it was showed that the methanolic and n-Butanol extracts contains the highestportion of glycosylic steroid saponins in comparison to other fractions. Regarding experimental autoimmune encephalomyelitis (EAE) score, Butanolic and methanolic fractions with doses higher that 100mg/kg showed a potent supportive effects as long as locomotor activity protection even in lower dose in comparison to phosphate buffered saline (PBS) group.

Conclusion

Considering the proved different effects of saponin compounds on the immune system we observed that those fractions altered the circulatory peripheral blood cells and also remit the clinical signs after EAE induction along with enhanced myelin sheath content in the median region of corpus callusom. It could be inferred that this fractions are promising candidates for further investigation as dose-dependent immune system regulating compounds in multiple sclerosis patients.

Comparative transcriptome analysis reveals key genes for polyphyllin difference in five Paris species

Paris species accumulate a large amount of steroidal saponins, which have numerous pharmacological activities and have become an essential component in many patented drugs. However, only two among all Paris species. Paris are identified as official sources due to high level of bioactive compounds. To clarify the composition of steroidal saponins and the molecular basis behind the differences between species, we investigated transcriptome and metabolic profiles of leaves and rhizomes in Paris polyphylla var. chinensis (PPC), Paris polyphylla var. yunnanensis (PPY), Paris polyphylla var. stenophylla (PPS), Paris fargesii (PF), and Paris mairei (PM). Phytochemical results displayed that the accumulation of steroidal saponins was tissue- and species-specific. PF and PPS contained more steroidal saponins in leaves than rhizomes, while PPY accumulated more steroidal saponins in rhizomes than leaves. PPC and PM contained similar amounts of steroidal saponins in leaves and rhizomes. Transcriptome analysis illustrated that most differentially expressed genes related to the biosynthesis of steroidal saponins were abundantly expressed in rhizomes than leaves. Meanwhile, more biosynthetic genes had significant correlations with steroidal saponins in rhizomes than in leaves. The result of CCA indicated that ACAT, DXS, DWF1, and CYP90 constrained 97.35% of the variance in bioactive compounds in leaves, whereas CYP72, UGT73, ACAT, and GPPS constrained 98.61% of the variance in phytochemicals in rhizomes. This study provided critical information for enhancing the production of steroidal saponins by biotechnological approaches and methodologies.

Astragalus species: Phytochemistry, biological actions and molecular mechanisms underlying their potential neuroprotective effects on neurological diseases

Neurodegenerative and neuropsychiatric illnesses are prevalent and life-threatening disorders characterized by a wide range of clinical syndromes and comorbidities, all of which have complex origins and share common molecular pathomechanisms. Although the pathophysiology of neurological illnesses is not completely understood, researchers have discovered that several ion channels and signalling pathways may have played a role in disease pathogenesis. Active substances from Astragalus sp. are being employed for nutrition, and their usefulness in the treatment of neurological illnesses is receiving more attention. Because their extracts and active components exert different pharmacological effects on a variety of ailments, they have a long history of usage as a cure for various diseases. This review summarizes the research work on Astragalus and their biologically active constituents as potential candidates for the protection against and treatment of neurodegenerative and neuropsychiatric disorders to show the potential efficacy of Astragalus sp. and its active ingredients in treating some neurological diseases. Simultaneously, the chemical structures of these active compounds, their sources, biological properties, and mechanisms are also listed. In ethnopharmacological applications, Astragalus membranaceus and spinosus have been studied as traditional medicines worldwide. The chemical constituents of Astragalus species mainly comprise terpenoids, flavonoids, and polysaccharides. The extracts and phytochemical compounds of Astragalus species exhibit various pharmacological activities, including antioxidant, anti-inflammatory, anticancer, antitumor, anticonvulsive, immunomodulatory, and other activities. Based on the current literature, we conclude that Astragalus is a promising dietary herb with multiple potential signal modulating applications that mainly include the modulation of neurotransmitters and receptors, anti-inflammatory activities, inhibition of amyloid aggregation, induction of myelin sheath repair and neurogenesis, as well as activation of the signalling pathways relevant to neurological diseases.

Characterization of Three Paris polyphylla Glycosyltransferases from Different UGT Families for Steroid Functionalization

Plant steroid glycosides, such as phytosterol glycosides, steroidal saponins, and steroidal glycoalkaloids, are natural products with great pharmaceutical values. In this study, we characterized three UDP-glycosyltransferases (UGTs) involved in the glycosylation of steroidal sapogenin from Paris polyphylla. Substrate specificity analysis revealed that UGT73CR1 could glycosylate steroidal sapogenins and steroidal alkaloids, with the highest affinity for diosgenin. The residues His27 and Asp129 of UGT73CR1 are conserved in corresponding positions of plant glycosyltransferases, which are crucial for activating the C-3 OH of the receptor substrates. In comparison, UGT80A33 and UGT80A34 exhibited a higher affinity for cholesterol than other steroids. UGT80s have a larger active pocket, which allows them to accommodate the side chain of sterols. In summary, we assessed three P. polyphylla glycosyltransferases from two UGT families for the functionalization of steroidal molecules, which will provide a basis for the future biomanufacturing of diverse bioactive steroid glycosides.

The isolation of water-soluble natural products - challenges, strategies and perspectives

Covering period: up to 2019Water-soluble natural products constitute a relevant group of secondary metabolites notably known for presenting potent biological activities. Examples are aminoglycosides, β-lactam antibiotics, saponins of both terrestrial and marine origin, and marine toxins. Although extensively investigated in the past, particularly during the golden age of antibiotics, hydrophilic fractions have been less scrutinized during the last few decades. This review addresses the possible reasons on why water-soluble metabolites are now under investigated and describes approaches and strategies for the isolation of these natural compounds. It presents examples of several classes of hydrosoluble natural products and how they have been isolated. Novel stationary phases and chromatography techniques are also reviewed, providing a perspective towards a renaissance in the investigation of water-soluble natural products.

Bulbous Plants Drimia: "A Thin Line between Poisonous and Healing Compounds" with Biological Activities

Drimia (synonym Urginea) plants are bulbous plants belonging to the family Asparagaceae (formerly the family Hyacinthaceae) and are distinctive, powerful medicinal plants. Just some species are indigenous to South Africa and have been traditionally utilized for centuries to cure various diseases and/or ailments. They have been recognized among the most famous and used medicinal plants in South Africa. Traditionally, the plants are used for various illnesses such as dropsy, respiratory disease, bone and joint complications, skin disorders, epilepsy and cancer. A number of studies have reported biological properties such as antiviral, antibacterial, antioxidant and anti-inflammatory, immunomodulatory, and anticancer activities. Their bulbs are a popular treatment for colds, measles, pneumonia, coughs, fever and headaches. However, some plant species are regarded as one of the six most common poisonous plants in Southern Africa that are toxic to livestock and humans. Due to the therapeutic effects of the Drimia plant bulb, research has focused on the phytochemicals of Drimia species. The principal constituents isolated from this genus are cardiac glycosides. In addition, phenolic compounds, phytosterols and other phytochemical constituents were identified. This study constitutes a critical review of Drimia species' bioactive compounds, toxicology, biological properties and phytochemistry, advocating it as an important source for effective therapeutic medicine. For this purpose, various scientific electronic databases such as ScienceDirect, Scopus, Google Scholar, PubMed and Web of Science were researched and reviewed to conduct this study. Despite well-studied biological investigations, there is limited research on the toxic properties and the toxic compounds of certain Drimia species. Searching from 2017 to 2021, Google Scholar search tools retrieved 462 publications; however, only 3 investigated the toxicity and safety aspects of Drimia. The aim was to identify the current scientific research gap on Drimia species, hence highlighting a thin line between poisonous and healing compounds, dotted across numerous publications, in this review paper.

Cloning and Functional Characterization of a Squalene Synthase from Paris polyphylla var. yunnanensis

Paris polyphylla Smith var. yunnanensis (Franch.) Hand. - Mazz. is a precious traditional Chinese medicine, and steroidal saponins are its major bioactive constituents possessing extensive biological activities. Squalene synthase (SQS) catalyzes the first dedicated step converting two molecular of farnesyl diphosphate (FDP) into squalene, a key intermediate in the biosynthetic pathway of steroidal saponins. In this study, a squalene synthase gene (PpSQS1) was cloned and functionally characterized from P. polyphylla var. yunnanensis, representing the first identified SQS from the genus Paris. The open reading frame of PpSQS1 is 1239 bp, which encodes a protein of 412 amino acids showing high similarity to those of other plant SQSs. Expression of PpSQS1 in Escherichia coli resulted in production of soluble recombinant proteins. Gas chromatography-mass spectrometry analysis showed that the purified recombinant PpSQS1 protein could produce squalene using FDP as a substrate in the in vitro enzymatic assay. qRT-PCR analysis indicated that PpSQS1 was highly expressed in rhizomes, consistent with the dominant accumulation of steroidal saponins there, suggesting that PpSQS1 is likely involved in the biosynthesis of steroidal saponins in the plant. The findings lay a foundation for further investigation on the biosynthesis and regulation of steroidal saponins, and also provide an alternative gene for manipulation of steroid production using synthetic biology.

Phytochemicals and Biological Activity of Desert Date (Balanites aegyptiaca (L.) Delile)

Many underutilized tree species are good sources of food, fodder and possible therapeutic agents. Balanites aegyptiaca (L.) Delile belongs to the Zygophyllaceae family and is popularly known as “desert date”, reflecting its edible fruits. This tree grows naturally in Africa, the Middle East and the Indian subcontinent. Local inhabitants use fruits, leaves, roots, stem and root bark of the species for the treatment of various ailments. Several research studies demonstrate that extracts and phytochemicals isolated from desert date display antioxidant, anticancer, antidiabetic, anti-inflammatory, antimicrobial, hepatoprotective and molluscicidal activities. Mesocarp of fruits, seeds, leaves, stem and root bark are rich sources of saponins. These tissues are also rich in phenolic acids, flavonoids, coumarins, alkaloids and polysterols. Some constituents show antioxidant, anticancer and antidiabetic properties. The objective of this review is to summarize studies on diverse bioactive compounds and the beneficial properties of B. aegyptiaca.

A spirostanol saponin isolated from Tupistra chinensis Baker simultaneously induces apoptosis and autophagy by regulating the JNK pathway in human gastric cancer cells

T-17, a bioactive spirostanol saponin extracted from Tupistra chinensis Baker, was previously reported with anti-inflammatory and cytotoxic activities. However, the mechanism underlying of its anti-proliferation activity remains to be elucidated. In this study, we investigated the anti-gastric cancer cell growth activity of T-17 in terms of cell viability, colony formation, cell cycle, induction of apoptosis/autophagy, and JNK pathway. T-17 showed dose-dependent cytotoxicity in SGC-7901 and AGS cell lines, it induced caspase-mediated apoptosis as well as G0/G1 phase arrest and modulation of cyclinE2 and p21 expression. In addition, T-17 promoted the cancer cell autophagy as evidenced with increased expression of Beclin-1 and decreased p62 in western blot and formation of GFP-LC3 puncta. Furthermore, T-17-induced autophagy decreased gastric cancer cell apoptosis as assessed by pharmacological autophagy inhibitors and ATG5 siRNA usage. Importantly, the activation of JNK pathway was simultaneously involved in T-17-induced apoptosis and autophagy. Taken together, the results suggest that T-17 is a promising cytotoxic agent for therapeutic treatment of human gastric adenocarcinoma, which provides a good foundation for further research and development of Tupistra chinensis Baker.

Lanostane-Type Saponins from Vitaliana primuliflora

The phytochemistry of the genera Androsace, Cortusa, Soldanella, and Vitaliana, belonging to the Primulaceae family is not well studied so far. Hence, in this paper, we present the results of UHPLC-MS/MS analysis of several primrose family members as well as isolation and structure determination of two new saponins from Vitaliana primuliflora subsp. praetutiana. These two nor-triterpenoid saponins were characterized as (23S)-17α,23-epoxy-29-hydroxy-3β-[(O-β-d-glucopyranosyl-(1→2)-O-α-l-rhamnopyranosyl-(1→2)-O-β-d-glucopyranosyl-(1→2)-O-α-l-arabinopyranosyl-(1→6)-β-d-glucopyranosyl)oxy]-27-nor-lanost-8-en-25-one and (23S)-17α,23-epoxy-29-hydroxy-3β-[(O-α-l-rhamnopyranosyl-(1→2)-O-β-d-glucopyranosyl-(1→2)-O-α-l-arabinopyranosyl-(1→6)-β-d-glucopyranosyl)oxy]-27-nor-lanost-8-en-25-one, respectively. Their structures were determined by high resolution mass spectrometry (HRMS), tandem mass spectrometry (MS/MS), one- and two-dimensional nuclear magnetic resonance spectroscopy (1D-, and 2D-NMR) analyses. So far, the 27-nor-lanostane monodesmosides were rarely found in dicotyledon plants. Therefore their presence in Vitaliana and also in Androsace species belonging to the Aretia section is unique and reported here for the first time. Additionally, eleven other saponins were determined by HRMS and MS/MS spectra. The isolated lanostane saponins can be considered as chemotaxonomic markers of the family Primulaceae.

Phytoestrogens, phytosteroids and saponins in vegetables: Biosynthesis, functions, health effects and practical applications

Phytoestrogens are non-steroidal secondary metabolites with similarities in structure and biological activities with human estrogens divided into various classes of compounds, including lignans, isoflavones, ellagitannins, coumestans and stilbenes. Similarly, phytosteroids are steroidal compounds of plant origin which have estrogenic effects and can act as agonists, antagonists, or have a mixed agonistic/antagonistic activity to animal steroid receptors. On the other hand, saponins are widely distributed plant glucosides divided into triterpenoid and steroidal saponins that contribute to plant defense mechanism against herbivores. They present a great variation from a structural point of view, including compounds from different classes. In this chapter, the main vegetable sources of these compounds will be presented, while details regarding their biosynthesis and plant functions will be also discussed. Moreover, considering the significant bioactive properties that these compounds exhibit, special focus will be given on their health effects, either beneficial or adverse. The practical applications of these compounds in agriculture and phytomedicine will be also demonstrated, as well as the future prospects for related research.

Approaches for the isolation and identification of hydrophilic, light-sensitive, volatile and minor natural products

Water-soluble, volatile, minor and photosensitive natural products are yet poorly known, and this review discusses the literature reporting the isolation strategies for some of these metabolites.

Synthesis and antiproliferative activities of OSW-1 analogues bearing 2-acylamino-xylose residues

We synthesized 38 OSW-1 analogues with 2-acylamino xylose residues and found that the antitumor activities could be greatly enhanced.

Recent advances in steroidal saponins biosynthesis and in vitro production

Steroidal saponins exhibited numerous pharmacological activities due to the modification of their backbone by different cytochrome P450s (P450) and UDP glycosyltransferases (UGTs). Plant-derived steroidal saponins are not sufficient for utilizing them for commercial purpose so in vitro production of saponin by tissue culture, root culture, embryo culture, etc, is necessary for its large-scale production. Saponin glycosides are the important class of plant secondary metabolites, which consists of either steroidal or terpenoidal backbone. Due to the existence of a wide range of medicinal properties, saponin glycosides are pharmacologically very important. This review is focused on important medicinal properties of steroidal saponin, its occurrence, and biosynthesis. In addition to this, some recently identified plants containing steroidal saponins in different parts were summarized. The high throughput transcriptome sequencing approach elaborates our understanding related to the secondary metabolic pathway and its regulation even in the absence of adequate genomic information of non-model plants. The aim of this review is to encapsulate the information related to applications of steroidal saponin and its biosynthetic enzymes specially P450s and UGTs that are involved at later stage modifications of saponin backbone. Lastly, we discussed the in vitro production of steroidal saponin as the plant-based production of saponin is time-consuming and yield a limited amount of saponins. A large amount of plant material has been used to increase the production of steroidal saponin by employing in vitro culture technique, which has received a lot of attention in past two decades and provides a way to conserve medicinal plants as well as to escape them for being endangered.

Organo-Catalyzed Asymmetric Michael-Hemiketalization-Oxa-Pictet-Spengler Cyclization for Bridged and Spiro Heterocyclic Skeletons: Oxocarbenium Ion as a Key Intermediate

A Michael-hemiketalization-oxa-Pictet-Spengler cyclization has been developed for the construction of chiral bridged and spiro heterocyclic skeletons with one spiro stereogenic carbon center and two bridgehead carbon centers, utilizing cooperative catalysts of a Takemoto thiourea catalyst and a triflimide. In particular, an oxocarbenium ion acts as a key intermediate for this cyclization reaction. Additionally, biological evaluation of this type of novel structure has revealed obvious antiproliferative activity against some cancer cell lines.

Steroidal Saponins from the Genus Smilax and Their Biological Activities

The Smilax species, widely distributed in tropical region of the world and the warm areas of East Asia and North America, are extensively used as folk medicine to treat inflammatory disorders. Chemical investigation on Smilax species showed they are rich sources of steroidal saponins with diversified structure types, including spirostane, isospirostane, furostane, pregnane, and cholestane. This review mainly summarizes the steroidal saponins (1-104) reported from the genus Smilax between 1967 and 2016, and their biological activities. The relationship between structures of steroidal saponins and related biological activities were briefly discussed.

Isolation and characterization of Cepa2, a natural alliospiroside A, from shallot (Allium cepa L. Aggregatum group) with anticancer activity

Exploration of new and promising anticancer compounds continues to be one of the main tasks of cancer research because of the drug resistance, high cytotoxicity and limitations of tumor selectivity. Natural products represent a better choice for cancer treatment in comparison with synthetic compounds because of their pharmacokinetic properties and lower side effects. In the current study, we isolated a steroidal saponin, named Cepa2, from the dry roots of shallot (Allium cepa L. Aggregatum group), and determined its structure by using two-dimensional nuclear manganic resonance (2D NMR). The ¹H NMR and ¹³C NMR data revealed that the newly isolated Cepa2 compound is identical to alliospiroside A (C₃₈H₆₀O₁₂) [(25S)-3β-hydroxyspirost-5-en-1β-yl-2-O-(6-deoxy-α-L-mannopyranosyl)-α-L-arabinopyranoside], whose anticancer activity remains elusive. Our in vitro examination of the cytotoxic activity of the identified Cepa2 against P3U1 myeloma cancer cell line showed its high efficiency as an anticancer with 91.13% reduction in P3U1 cell viability 12 h post-treatment. The reduction of cell viability was correlated with the increase in reactive oxygen species levels in Cepa2-treated P3U1 cells, as compared with untreated cells. Moreover, scanning electron microscope results demonstrated apoptosis of the Cepa2-treated P3U1 cells in a time course-dependent manner. The results of our study provide evidence for the anticancer properties of the natural Cepa2/alliospiroside A extracted from shallot plants, and a strong foundation for in-depth investigations to build theoretical bases for cell apoptosis and development of novel anticancer drugs.

A small plant with big benefits: Fenugreek (Trigonella foenum-graecum Linn.) for disease prevention and health promotion

Plant-derived natural products have long-standing utility toward treating degenerative diseases. It is estimated that about two-thirds of world population depend on traditional medicine for primary medical needs. Fenugreek (Trigonella foenum-graecum Linn.), a short-living annual medicinal plant belonging to Fabaceae family, is used extensively in various parts of the world as herb, food, spice, and traditional medicine. Fenugreek is considered as one of the oldest medicinal plants and its health-promoting effects have been cited in Ayurveda and traditional Chinese medicine. The investigations into the chemical composition and pharmacological actions have seen a renaissance in recent years. Extensive preclinical and clinical research have outlined the pharmaceutical uses of fenugreek as antidiabetic, antihyperlipidemic, antiobesity, anticancer, anti-inflammatory, antioxidant, antifungal, antibacterial, galactogogue and for miscellaneous pharmacological effects, including improving women's health. The pharmacological actions of fenugreek are attributed to diverse array of phytoconstituents. The phytochemical analysis reveals the presence of steroids, alkaloids, saponins, polyphenols, flavonoids, lipids, carbohydrates, amino acids, and hydrocarbons. This review aims to summarize and critically analyze the current available literature to understand the potential of fenugreek for disease prevention and health improvement with special emphasis on cellular and molecular mechanisms. Current challenges and new directions of research on fenugreek are also discussed.

Effect of Hecogenin on DNA instability

Hecogenin is a sapogenin found in Agave species in high quantities and is responsible for the many therapeutic effects of these medicinal plants. In addition, this compound is also widely used in the pharmaceutical industry as a precursor for the synthesis of steroidal hormones and anti-inflammatory drugs. Despite Hecogenin being widely used, little is known about its toxicological properties. Therefore, the present study aimed to investigate the cytotoxic, genotoxic and mutagenic effects of Hecogenin on HepG2 cells. Cytotoxicity was analyzed using the MTT test. Then, genotoxic and mutagenic potentials were assessed by comet assay and cytokinesis-block micronucleus assay, respectively. Cytotoxic effect was observed only when cells were exposed to concentrations of Hecogenin equal or higher than 100 μM. Although a lower concentration of Hecogenin caused DNA damage, a reduction on nuclear mutagenic markers in HepG2 cells was observed. The results indicated that Hecogenin treatment generated DNA damage, but in fact it would be repaired, avoiding dissemination of the damage throughout the cell division. Further studies need to be performed to confirm the observed protective effect of Hecogenin against genomic instability.

Self-organizing behaviour of glycosteroidal bolaphiles: insights into lipidic microsegregation

In this article we describe work on the synthesis of bolaphile biomimics composed of glucose head groups and steroidal units linked together by a methylene chain of varying length. The condensed phases formed by self-organization of the products as a function of temperature were characterized by differential scanning calorimetry and thermal polarized light microscopy. The results of these studies show that the thermal stabilities of the lamellar mesophases formed vary linearly as a function of increasing aliphatic composition, which reflects a linear hydrophobic-hydrophilic balance with respect to transition temperatures.

Plant Chemical Defenses: Are all Constitutive Antimicrobial Metabolites Phytoanticipins?

A critical perspective on phytoanticipins, constitutive plant secondary metabolites with defensive roles against microbes is presented. This mini-review focuses on the chemical groups and structural types of defensive plant metabolites thus far not reviewed from the phytoanticipin perspective: i) fatty acid derivatives and polyketides, ii) terpenoids, iii) shikimates, phenylpropanoids and derivatives, and iv) benzylisoquinoline and pyrrolizidine alkaloids. The more traditional groups of phytoanticipins are briefly summarized, with particular focus on the latest results: i) benzoxazinoids, ii) cyanogenic glycosides, iii) glucosinolates and their metabolic products, and iv) saponins. Current evidence suggests that a better understanding of the functions of plant metabolites will drive their application to protect crops against microbial diseases.

Karataviosides G-K, five new bisdesmosidic steroidal glycosides from the bulbs of Allium karataviense

We have analyzed the steroidal glycosides in Allium karataviense bulbs, and isolated five new bisdesmosidic steroidal glycosides: karataviosides G-K (1-5). The structures were elucidated by extensive spectroscopic analysis, including 2D NMR and enzymatic and hydrolytic cleavage. Karatavioside G (1) is an entirely novel furostanol glycoside, which has an O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranosyl-(1→6)-β-d-glucopyranosyl unit at C-26 of the aglycone. Although a variety of cholestanol glycosides have been isolated, mainly from Liliaceae and Agavaceae, karataviosides J and K (4 and 5) are also notable because they are the most polar cholestanol bisdesmosides discovered, in which a lycotetraose is attached to C-3 of the aglycone, and a glucose or O-glucosyl-(1→3)-glucose is attached at C-16. The isolated glycosides were also evaluated for their cytotoxic activities against cultured tumor cell lines.

Separation and purification of steroidal saponins from Paris polyphylla by microwave-assisted extraction coupled with countercurrent chromatography using evaporative light scattering detection

A method of microwave-assisted extraction coupled with countercurrent chromatography using evaporative light scattering detection was successfully developed for the separation and purification of steroidal saponins from Paris polyphylla. The main extraction conditions including microwave power, liquid/solid ratio, irradiation time, and extraction temperature were optimized using an orthogonal array design method. A suitable two-phase solvent system consisting of n-heptane/n-butanol/acetonitrile/water (10:19:6:20, v/v/v/v) was employed in the separation and purification of the extracts of P. polyphylla. A total of 7.1 mg polyphyllin VII, 4.3 mg gracillin, 9.2 mg dioscin, and 10.2 mg polyphyllin I were obtained from 1.5 g P. polyphylla in less than 300 min, the purities of which determined by HPLC were 96.7, 97.3, 98.7, and 98.6%, respectively. The identification and characterization of these compounds were performed by LC-ESI-MS and 1H NMR spectroscopy. The results demonstrated that the proposed method is feasible, economical and efficient for the extraction, separation and purification of effective compounds from natural products.

Steroidal saponins from the genus Allium

Steroidal saponins are widely distributed among monocots, including the Amaryllidaceae family to which the Allium genus is currently classified. Apart from sulfur compounds, these are important biologically active molecules that are considered to be responsible for the observed activity of Allium species, including antifungal, cytotoxic, enzyme-inhibitory, and other. In this paper, literature data concerning chemistry and biological activity of steroidal saponins from the Allium genus has been reviewed.

Isolation and structural elucidation of novel cholestane glycosides and spirostane saponins from Polygonatum odoratum

Much attention has been paid to cholestane-type steroidal glycosides because of their importance from the perspectives of both chemical diversity and significant biological activities. A phytochemical investigation of the rhizomes of Polygonatum odoratum (Liliaceae) resulted in the isolation of three novel cholestane-type steroidal glycosides (1-3) with unique Δ(14,16)-unsaturated D-ring structures as well as two novel spirostane-type steroidal saponins (4 and 5) and three known steroidal glycosides (6-8). Their structures were determined by various spectroscopic methods and chemical reactions. Steroidal saponin 7 showed significant antifungal activity against Candida albicans JCM1542 (MIC 3.1 μg/mL) and Aspergillus fumigatus JCM1738 (MIC 6.3 μg/mL).

Spirostane, furostane and cholestane saponins from Persian leek with antifungal activity

A phytochemical investigation of the seeds of Persian leek afforded the isolation of two new spirostane glycosides, persicosides A (1) and B (2), four new furostane glycosides, isolated as a couple of inseparable mixture, persicosides C1/C2 (3a/3b) and D1/D2 (4a/4b), one cholestane glycoside, persicoside E (5), together with the furostane glycosides ceposides A1/A2 and C1/C2 (6a/6b and 7a/7b), tropeosides A1/A2 and B1/B2 (8a/8b and 9a/9b), and ascalonicoside A1/A2 (10a/10b), already described in white onion, red Tropea onion, and shallot, respectively. Structure elucidation of the compounds was carried out by comprehensive spectroscopic analyses, including 2D NMR spectroscopy and MS spectrometry, and by chemical evidences. The chemical structure of new compounds were identified as (25S)-spirostan-2α,3β,6β-triol 3-O-[β-d-glucopyranosyl-(1→3)] [β-d-xylopyranosyl-(1→2)]-β-d-glucopyranosyl-(1→4)-β-d-galactopyranoside (1), (25S)-spirostan-2α,3β,6β-triol 3-O-[β-d-xylopyranosyl-(1→3)] [α-l-rhamnopyranosyl-(1→2)]-β-d-glucopyranosyl-(1→4)-O-β-d-galactopyranoside (2), furosta-1β,3β,22ξ,26-tetraol 5-en 1-O-β-d-glucopyranosyl (1→3)-β-d-glucopyranosyl (1→2)-β-d-galactopyranosyl 26-O-α-l-rhamnopyranosyl (1→2)-β-d-galactopyranoside (3a,3b), furosta-2α,3β,22ξ,26-tetraol 3-O-β-d-glucopyranosyl (1→3)-β-d-glucopyranosyl (1→2)-β-d-galactopyranosyl 26-O-β-d-glucopyranoside (4a,4b), (22S)-cholesta-1β,3β,16β,22β-tetraol 5-en 1-O-α-l-rhamnopyranosyl 16-O-α-l-rhamnopyranosyl (1→2)-β-d-galactopyranoside (5). Antifungal activity of the isolated compounds was evaluated against the fungal pathogens, Penicillium italicum, Aspergillus niger, Trichoderma harzianum and Botrytis cinerea. Persicosides A and B showed the higher activity on the tested fungi highlighting the positive effect of the spirostane skeleton on the antifungal activity.